(1) Field of the Invention
The present invention pertains to a photopolymer washout fluid solvent distillation apparatus and method. In particular, the present invention pertains to an apparatus used in distilling and recovering a desired solvent from waste photopolymer- washout fluid and to the method of the apparatus' operation. The apparatus adds a surrogate solvent to the photopolymer waste fluid as the desired solvent is distilled from the waste fluid, thereby enabling recovery of a greater percentage of the desired solvent from the waste fluid while maintaining the liquidity of the waste fluid.
(2) Description of the Related Art
Known prior art methods of producing printing plates from acrylic elastomer resins and synthetic rubber plates include photoengraving and chemical milling of plate material to produce the printing plates. In these prior art processes, a layer of photoresist is applied over a surface of the plate material. The photoresist layer is then exposed to light through a photographic film or a masking stencil having a pattern formed therein corresponding to a desired pattern to be formed on the printing plate.
Exposure of the layer of photoresist to the electromagnetic radiation through the stencil or photographic film alters the susceptibility of the photoresist layer to removal by a photopolymer plate washout fluid. Applying the photopolymer plate washout fluid to the photoresist layer and the plate material removes the resist and etches away the plate material in a reverse pattern corresponding to the stencil or photographic film. The acrylic elastomer or synthetic rubber particles etched from the plate making material are washed away with the waste photopolymer washout fluid.
In order to more efficiently produce printing plates according to the process described above, it is desirable to recover the solvent employed as the photopolymer plate washout fluid by removing the acrylic elastomer particles and other foreign particles from the washout fluid. Until recently, a dominant washout fluid used in the plate making industry was alcohol-perchloroethylene. Older solvent distillation units, designed and installed without a vacuum assist, could recover and recycle these low boiling point "perc" solvents. New regulations, however, have led washout solution suppliers to develop new "safe solvents". These high-boiling point solvents require a vacuum assist distillation system in order to recover the solvents, and almost all prior art recovery systems cannot be adapted for vacuum assist.
In addition, most prior art solvent recovery distillation systems have small capacities that are unable to service larger plate processors that produce wider plates and a greater amount of waste washout fluid. In these prior art distillation systems, a flexible bag is typically suspended inside a distillation tank. The waste photopolymer washout fluid is then supplied into the bag and the desired solvent is distilled from the washout fluid while it is in the bag. The washout fluid is distilled until it is reduced to an amorphous solid. When the distillation process reaches this point, the bag containing the amorphous solid is removed from the distillation tank and disposed of. In this prior art method of distilling desired solvents from waste photopolymer washout fluids, it is possible to recover about 85% of the desired solvent from a sample of waste washout fluid. Because the bags containing the reduced amorphous solid waste are removed from the distillation tank interior by the operator of the apparatus, the capacities of the system must be kept small to enable the bag containing the amorphous solid to be removed from the tank interior.
What is needed to overcome disadvantages associated with prior art photopolymer waste washout fluid recovery systems is a photopolymer waste fluid distillation system that is capable of processing large amounts of waste fluid and recovering more than 85% of the desired solvent from the waste fluid, while facilitating the disposal of the waste residue left after the desired solvent has been recovered. The distillation system should reduce emissions from the waste fluid processed and reduce the incidence of operator contact with the waste fluid being processed. What is also needed is a desired solvent recovery apparatus that is constructed in a manner that enables it to be easily connected with existing plate processors of various types to receive waste photopolymer washout fluid from the existing plate processor equipment and return recovered solvent to the equipment.